Known prior art such as U.S. Pat. No. 3,672,017 to Nielsen et al. and U.S. Pat. No. 4,472,093 to Hamilton disclose tools having curved cutting inserts and scalloped cutting inserts. Such inserts have the following draw backs:
a)difficult to make, PA1 b) because of the curvatures it is difficult to evenly wedge the insert in the associated tool thus resulting in uneven forces and pressures on the insert which results in breakage and a shortened insert life, and PA1 c) the inserts have to be ground while in the operating tool; the inserts can not be taken out of the operating tool, ground and then replaced.
Another patent of interest with respect to the inventive concept is U.S. Pat. No. 5,325,748 to Ehrenberg which discloses a tool having one single straight bar cutting insert offset from the longitudinally axis of the tool to provide a helical cutting action. The Ehrenberg tools provide a single cutting action during rotation of the tool. For high speed operations, it has been found necessary to have a milling tool with a number of cutting inserts or blades on its periphery. For example, the inventive tool is operable at 22,000 rpm while the single insert Ehrenberg tool can not be satisfactorily operated above 13,000 rpm. One reason for this is that in the Ehrenberg tool a single off-center insert is mounted on the periphery of the tool, and therefore the tool is not balanced. Further, the structure of the Ehrenberg can not provide even two cutting inserts, since any additional inserts mounted on the tool would destroy the tool shank.